IBM System/36

A mid-range computer introduced in 1983, which
remained popular in the 1990s because of its low cost and high
performance. Prices started in the $20k range for the small
5362 to $100+k for the expanded 5360. In 1994, IBM introduced
the Advanced 36 for $9,000.

The largest 5360 had 7MB of RAM and 1432MB of hard disk.
The smallest 5362 had 256K of RAM and 30MB of hard disk. The
Advanced 36 had 64MB of RAM and 4300MB of hard disk, but
design issues limit the amount of storage that can actually be
addressed by the operating system; underlying microcode
allowed additional RAM to cache disk reads and writes,
allowing the Advanced 36 to outperform the S/36 by 600 to
800%.

There was only one operating system for the S/36: SSP (System
Support Product). SSP consumed about 7-10MB of hard drive
space. Computer programs on the S/36 reside in "libraries,"
and the SSP itself resides in a special system library called
#LIBRARY.

Using the IBM S/36 is relatively simple. The operator sits in
front of a computer monitor, types on a keyboard, and
interacts using a series of on-screen forms. S/36 is
command-oriented, like MS-DOS, however, S/36 additionally uses
more than 70 menus which allow operators to type the number of
an appropriate command or response, and application writers
can create their own menus and commands ("procedures.")

Programmers use SEU to create or modify a source program
which is then compiled into an object program. SEU uses 50
or so templates to assist the operator with the syntax of
different types of sources.

By 1985, an application called Programmer/Operator
Productivity was widely available and was probably the most
popular (and pirated) S/36 software ever written. POP
included a full-screen editor called FSEDIT which could be
used in place of SEU, which only allowed single-line editing.

Data File Utility allows the programmer to quickly create a
simple, single-record display program to add, update and
delete records within a file. Also, simple report programs
can be created.

By using Operational Control Language, the programmer can
assign files and resources to a particular program and pass
run-time information like a processing date, order number, or
user name to the compiled program. Programs can acquire up to
8 workstations, or run in the background, but usually they run
on only one workstation. The largest program size is 64K.

Whenever a program is called, SSP searches in the named user
library and then #LIBRARY. Therefore, a system program can be
called from any library and all users have access to it.

S/36 has three types of security: (1) password security, (2) a
badge reader option that almost no-one ever bought, and (3)
resource security. There are five levels of users access and
five levels of resource access. By using password and
resource security effectively, the administrator (who was at
that time often called a DP Manager or Information Systems
Manager) can restrict access to critical and secure
applications.

The cheapest, and therefore most popular, language compiler
for the S/36 is RPG II, a language based on fixed logic
cycles which arose in the days of card readers. Other
languages include COBOL, FORTRAN and BASIC. Almost
every S/36 shop with in-house design uses RPG.

It's interesting to note that the S/36 allows the operator to
change a program while it is being used, which can be very
dangerous on live data. The S/38 and the iSeries computer do
not allow this.

IBM has not marketed the S/36 or Advanced 36 since 2000.
Price/performance of the AS/400 (aka iSeries) and hardware
technology of the present-generation PC makes the S/36 a
much less attractive offering from a different era in
computing.